Transcriptomic and proteomic profiling of human diabetic heart disease

 

Studies in animal models demonstrated the capability of type 2 diabetes (T2D) to induce cardiac dysfunction in the absence of vascular disease. However, whether and how T2D also impairs structure and function in human hearts remains poorly understood. Here, we performed transcriptional and proteomic profiling of left ventricular samples of 8 subjects with T2D, preserved EF (63,5%) and no history of ischemic heart disease (= diabetic cardiomyopathy; DbCM), 7 subjects with T2D, reduced EF (26,9%) and ischemic heart disease (= diabetic heart failure; DbHF), and 15 non-diabetic individuals with normal EF (64,7%) serving as controls. Among 1168 proteins identified by LC-MS/MS, 146 proteins were differentially regulated in DbHF, but only 66 in DbCM. Pathway analysis revealed downregulation of energy metabolic proteins, but upregulation of proteins involved in oxidative stress and inflammatory response. In DbCM, pathways of structural remodeling, cardiomyocyte proliferation, and mechanotransduction were upregulated. Bulk RNA sequencing revealed 1795 differentially regulated genes in DbHF, and 527 in DbCM, with only 128 genes being commonly regulated. DbHF, but not DbCM, could be clearly discriminated from controls by hierarchical clustering. While inflammation/immunity were major regulated pathways in DbHF, extracellular matrix remodeling and cellular growth were the most regulated pathways in DbCM. Thus, the differential regulation of biological pathways in DbCM versus DbHF suggests the existence of two distinct disease entities rather than DbHF being an advanced disease stage of DbCM.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Austrian Diabetes Society

Evaluation of the Assurance GDS™ for E. coli O157:H7 Method and Assurance GDS for Shigatoxin Genes Method in Selected Foods: Collaborative Study

A multilaboratory collaborative study was conducted to compare the Assurance GDS™ for E. coli O157:H7 method and the reference culture methods for the detection of E. coli O157:H7 in orange juice, raw ground beef, and fresh lettuce. A separate companion assay, the Assurance GDS for Shigatoxin Genes method was also evaluated with the same test portions. Fifteen laboratories participated in the study. A Chi square analysis of each of the 3 food types at the high, low, and uninoculated control levels was performed. For all foods, the Assurance GDS for E. coli O157:H7 method and the Assurance GDS for Shigatoxin Genes method were equivalent to or better than the reference methods.

Enumeration of Total Coliforms and E. coli in Foods by the SimPlate® Coliform and E. coli Color Indicator Method and Conventional Culture Methods: Collaborative Study

The relative effectiveness of the SimPlate® Coliform and E. coli Color Indicator (CEc-CI) method was compared to the AOAC 3-tube Most Probable Number (MPN) methods for enumerating and confirming coliforms and Escherichia coli in foods (966.23 and 966.24). In this study, test portions were prepared and analyzed according to the conditions stated in both the AOAC methods and SimPlate directions for use. Six food types were artificially contaminated with coliform bacteria and E. coli: frozen burritos, frozen broccoli, fluid pasteurized milk, whole almond nut meats, cheese, and powdered cake mix. Method comparisons were conducted. Overall, the SimPlate method demonstrated <0.3 log difference for total coliform and E. coli counts compared to the AOAC reference methods for the majority of food types and levels analyzed. In all cases, the repeatability and reproducibility of the SimPlate CEc-CI method were not different from those of the reference methods and in certain cases, were statistically better than those of the AOAC 3-tube MPN methods. These results indicate that the SimPlate CEc-CI method and the reference culture methods are comparable for enumeration of both total coliforms and E. coli in foods.

Liver Transplantation in a Patient at Psychosocial Risk

Psychosocial assessment of transplant candidates is a challenging task. Securing adequate information is made more difficult when patients present with fulminant hepatic failure. When the patient cannot be interviewed and the family is reluctant to provide vital information, a comprehensive pretransplant psychosocial evaluation is virtually impossible. However, even the most difficult cases have the potential for a positive result when a good psychosocial profile of the patient is obtained after transplantation, a team treatment plan is developed and carried out which addresses current and anticipated problems, and the patient obtains mental health treatment.

BRAF, NRAS and HRAS mutations in spitzoid tumours and their possible pathogenetic significance

BACKGROUND

The relationships between so-called spitzoid tumours have proven difficult to understand.

OBJECTIVES

To address three questions: does spitzoid tumour morphological similarity reflect molecular similarity? Does Spitz naevus progress into spitzoid melanoma? Are ambiguous spitzoid tumours genuine entities?

METHODS

BRAF, NRAS and HRAS mutations were analysed using single-strand conformational polymorphism analysis and sequencing.

RESULTS

Both Spitz naevi and spitzoid melanoma had a lower combined BRAF and NRAS mutation frequency compared with common acquired naevi (P = 0.0001) and common forms of melanoma (P = 0.0072), respectively. To look for evidence of progression from Spitz naevi to spitzoid melanoma, HRAS was analysed in 21 spitzoid melanomas, with no mutations identified. The binomial probability of this was 0.03 based on an assumption of a 15% mutation frequency in Spitz naevi with unbiased progression. Under these assumptions, HRAS mutations must be rare/absent in spitzoid melanoma. Thus, Spitz naevi seem unlikely to progress into spitzoid melanoma, implying that ambiguous spitzoid tumours cannot be intermediate degrees of progression. In addition, the data suggest that HRAS mutation is a potential marker of benign behaviour, in support of which none of three HRAS mutant spitzoid cases metastasized.

CONCLUSIONS

First, the morphological similarity of spitzoid tumours reflects an underlying molecular similarity, namely a relative lack of dependence on BRAF/NRAS mutations. Second, Spitz naevi do not appear to progress into spitzoid melanoma, and consequently ambiguous spitzoid tumours are likely to be unclassifiable Spitz naevi or spitzoid melanoma rather than genuine entities. Third, HRAS mutation may be a marker of Spitz naevus, raising the possibility that other molecular markers for discriminating Spitz naevi from spitzoid melanoma can be discovered.

Development of the functional capacity screening tool (FCST): A brief instrument to identify functional capacity deficits in anemic cancer patients

8593

Background: Existing fatigue measures are long and often difficult to incorporate in practice. The objective of this study was to develop a short tool (Functional Capacity Screening Tool [FCST]) to identify functional capacity deficits related to fatigue in anemic cancer patients (pts) using self-report and performance-based measures of functional capacity. Methods: Data were obtained from a multicenter, open-label, single-arm study of darbepoetin alfa therapy (3.0 μg/kg every 2 weeks) in cancer pts (n=1558) who were ≥ 18 years of age with nonmyeloid malignancies receiving cyclic chemotherapy and anemia (hemoglobin [Hb] ≤ 11 g/dL). The Modified Harvard Step Test (MHST) was used as a performance-based measure of functional capacity to assess adjusted VO2max. Pts who contributed data for the development of FCST completed the following: MHST, baseline and ≥ 1 follow-up Hb measurement, baseline and ≥ 1 follow-up Functional Assessment of Cancer Therapy-Fatigue (FACT-F), and fatigue assessed within 3 days of MHST. Items from FACT-F, Brief Fatigue Inventory (BFI), Fatigue Symptom Inventory (FSI) and Medical Outcomes Study physical functioning scale were tested for inclusion in the FCST. Individual item scores were transformed to a 100-point scale. Item selection was based on identifying best predictors of adjusted VO2max, Hb, and global FACT-F scores using linear regression and the r-square selection method. FCST scores were calculated by summating item scores and dividing by number of items. Results: Data from401 pts contributed to the development of the FCST. Eight items were identified for the FCST with a Cronbach’s coefficient alpha of 0.92. Construct validity was supported by correlations of FCST with FSI (r = 0.80, P < .0001) and BFI (r = 0.86, P < .0001). Correlations between FCST and energy (r = 0.75, P < .0001), productivity (r = 0.72, P < .0001), and Hb (r = 0.24, P < .0001) further supported construct validity. Conclusions: FCST holds promise as a short screening tool for identifying functional capacity deficits in cancer pts. This new instrument was reliable, easy to score, and completed quickly by pts, making it suitable for incorporation in clinical practice. Further validation is required in different cancer populations.

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A novel polymorphism in the 1A promoter region of the vitamin D receptor is associated with altered susceptibilty and prognosis in malignant melanoma

The association of Taq 1 and Fok 1 restriction fragment length polymorphisms of the vitamin D receptor with occurrence and outcome of malignant melanoma (MM), as predicted by tumour (Breslow) thickness, has been reported previously. We now report a novel adenine–guanine substitution −1012 bp relative to the exon 1a transcription start site (A-1012G), found following screening by single-stranded conformational polymorphism of this promoter region. There was a total of 191 MM cases , which were stratified according to conventional Breslow thickness groups, cases being randomly selected from each group to form a distribution corresponding to the known distribution of Breslow thickness in our area, and this population (n=176) was compared to 80 controls. The A allele was over-represented in MM patients and, with GG as reference, odds ratio (OR) for AG was 2.5, 95% confidence interval (CI) 1.1–5.7, (P=0.03) and AA 3.3, CI 1.4–8.1, (P=0.007). The outcome was known in 171 of 191 patients and the A allele was related to the development of metastasis, the Kaplan–Meier estimates of the probability of metastasis at 5 years being: GG 0%; AG 9%, CI 4–16%; AA 21%, CI 12–36%; (P=0.008), and to thicker Breslow thickness groups (P=0.04). The effect on metastasis was independent of tumour thickness and A-1012G may have predictive potential, additional to Breslow thickness. Neither the Fok 1 nor Taq 1 variants (f and t) were significantly related to the development of metastasis, although there was a strong relationship of fftt with the thickest Breslow thickness group (P=0.005). There was an interaction between the A-1012G and Fok 1 polymorphisms (P=0.025) and the Fok 1 variant enhanced the effect of the A allele of the A-1012G polymorphism on metastasis, the probability of metastasis for AAff at 5 years follow-up being 57%, CI 24–92%.

Nuclear beta-catenin in basal cell carcinoma correlates with increased proliferation

BACKGROUND

Virtually all BCCs have deregulation of the Hedgehog (Hh) signalling pathway and a proportion show nuclear beta-catenin accumulation. The latter is thought to be due to Hh pathway-directed Wnt expression but this has not been tested. An alternative cause of nuclear beta-catenin accumulation is gene mutation, which stabilizes the protein. Theoretically, reduced E-cadherin expression could also be important because it can sequester beta-catenin at the cell membrane. In turn, nuclear beta-catenin can increase expression of MYC and cyclin D1, thus potentially altering proliferation.

OBJECTIVES

To assess whether nuclear beta-catenin occurs in BCC, and to look at potential causes and consequences.

METHODS

Nuclear beta-catenin was assessed by immunohistochemistry, and its causes by analysis of E-cadherin expression, beta-catenin exon 3 mutation and WNT5A expression. Its consequences were assessed by analysing proliferation.

RESULTS

We found nuclear beta-catenin in 20 of 86 paraffin-embedded sections of BCCs using immunohistochemistry. BCCs showed increased WNT5A relative to the surrounding skin. No mutations in exon 3 of the beta-catenin gene were found in 10 cases. There was no association between beta-catenin localization and E-cadherin expression. Tumours with nuclear beta-catenin had significantly higher proliferation (P < 0.01).

CONCLUSIONS

The absence of beta-catenin gene mutations indicate that the Hh pathway-directed Wnt signalling remains the most likely cause of nuclear beta-catenin accumulation in BCC. Additionally, the correlation with increased proliferation is the first evidence that nuclear beta-catenin may have a biological effect. However, a causal link between Hh pathway deregulation, Wnt ligand overexpression, nuclear beta-catenin accumulation and increased proliferation remains to be confirmed.

Nitrate reduction in the periplasm of gram-negative bacteria

In contrast to the bacterial assimilatory and membrane-associated, respiratory nitrate reductases that have been studied for many years, it is only recently that periplasmic nitrate reductases have attracted growing interest. Recent research has shown that these soluble proteins are widely distributed, but vary greatly between species. All of those so far studied include four essential components: the periplasmic molybdoprotein, NapA, which is associated with a small, di-haem cytochrome, NapB; a putative quinol oxidase, NapC; and a possible pathway-specific chaperone, NapD. At least five other components have been found in different species. Other variations between species include the location of the nap genes on chromosomal or extrachromosomal DNA, and the environmental factors that regulate their expression. Despite the relatively small number of bacteria so far screened, striking correlations are beginning to emerge between the organization of the nap genes, the physiology of the host, the conditions under which the nap genes are expressed, and even the fate of nitrite, the product of Nap activity. Evidence is emerging that Nap fulfills a novel role in nitrate scavenging by some pathogenic bacteria.

School-associated violent deaths in the United States, 1994-1999

CONTEXT

Despite the public alarm following a series of high-profile school shootings that occurred in the United States during the late 1990s, little is known about the actual incidence and characteristics of school-associated violent deaths.

OBJECTIVE

To describe recent trends and features of school-associated violent deaths in the United States.

DESIGN, SETTING, AND SUBJECTS

Population-based surveillance study of data collected from media databases, state and local agencies, and police and school officials for July 1, 1994, through June 30, 1999. A case was defined as a homicide, suicide, legal intervention, or unintentional firearm-related death of a student or nonstudent in which the fatal injury occurred (1) on the campus of a public or private elementary or secondary school, (2) while the victim was on the way to or from such a school, or (3) while the victim was attending or traveling to or from an official school-sponsored event.

MAIN OUTCOME MEASURES

National estimates of risk of school-associated violent death; national trends in school-associated violent deaths; common features of these events; and potential risk factors for perpetration and victimization.

RESULTS

Between 1994 and 1999, 220 events resulting in 253 deaths were identified; 202 events involved 1 death and 18 involved multiple deaths (median, 2 deaths per multiple-victim event). Of the 220 events, 172 were homicides, 30 were suicides, 11 were homicide-suicides, 5 were legal intervention deaths, and 2 were unintentional firearm-related deaths. Students accounted for 172 (68.0%) of these deaths, resulting in an estimated average annual incidence of 0.068 per 100 000 students. Between 1992 and 1999, the rate of single-victim student homicides decreased significantly (P =.03); however, homicide rates for students killed in multiple-victim events increased (P =.047). Most events occurred around the start of the school day, the lunch period, or the end of the school day. For 120 (54.5%) of the incidents, respondents reported that a note, threat, or other action potentially indicating risk for violence occurred prior to the event. Homicide offenders were more likely than homicide victims to have expressed some form of suicidal behavior prior to the event (odds ratio [OR], 6.96; 95% confidence interval [CI], 1.96-24.65) and been bullied by their peers (OR, 2.57; 95% CI, 1.12-5.92).

CONCLUSIONS

Although school-associated violent deaths remain rare events, they have occurred often enough to allow for the detection of patterns and the identification of potential risk factors. This information may help schools respond to this problem.

Liver transplantation in a patient at psychosocial risk

Psychosocial assessment of transplant candidates is a challenging task. Securing adequate information is made more difficult when patients present with fulminant hepatic failure. When the patient cannot be interviewed and the family is reluctant to provide vital information, a comprehensive pretransplant psychosocial evaluation is virtually impossible. However, even the most difficult cases have the potential for a positive result when a good psychosocial profile of the patient is obtained after transplantation, a team treatment plan is developed and carried out which addresses current and anticipated problems, and the patient obtains mental health treatment.

Survival of bacteria during oxygen limitation

Regulatory mechanisms that enable bacteria associated with food, drinks and the human body to adapt to changes in the availability of oxygen are reviewed. Excess oxygen induces two adaptive responses to oxidative stress. Five or more control circuits enable enteric bacteria to generate energy and grow well in anaerobic environments. Two sets of enzymes catalyse both nitrate and nitrite reduction, and dual two-component regulatory systems sense and respond to the available nitrate and nitrite in the environment. The periplasmic nitrate reductase enables bacteria to scavenge low concentrations of nitrate: similar systems are found in food-borne and other pathogens.

Three years' experience of collaborative care pathways on a maxillofacial ward

Collaborative care pathways (CCPs) provide a framework for multidisciplinary patient care. They provide guidelines and a mechanism for audit, and were first introduced at the Regional Unit, Walton Hospital, Liverpool, in November 1994. They have been designed for many surgical groups. Between August 1996 and 31 July 1997, 955 patients were admitted on to the nine established pathways: fractured mandible (n=213), fractured zygoma (n=117), minor oral surgery (n=244), abscess (n=18), examination under anaesthesia (n=73), nasal surgery (n=73), osteotomy (n=80), salivary (n=63), and temporomandibular joint (n=74). The purpose of this article is to report the introduction of CCP in a maxillofacial ward and give results from a one-year audit. CCP have proved to be an extremely useful tool and have several advantages over traditional documentation. They are more accurate, easily computerized, and facilitate audit. They promote the development of guidelines and standardized perioperative care, and this in turn facilitates training and raises standards of care.

The managed care contract: survival or closure?

The managed health care contract can be considered the most powerful tool in the health care environment today. Providers of care as well as insurers need to fully comprehend the legal and financial impact of these contracts. Too many organizations (providers and insurers) are getting caught in financial failure, resulting in bottom line-driven health care. It seems that the days of providing the most ethically appropriate health care are gone. Too much emphasis has been put on providers and administrators to provide the care that will result in positive income. The only way to "protect" oneself is in the creation, negotiation, and administration of the managed health care contract.

An economic evaluation of levofloxacin versus cefuroxime axetil in the outpatient treatment of adults with community-acquired pneumonia

OBJECTIVE

To examine treatment costs of community-acquired pneumonia (CAP) in adult outpatients given oral (p.o.) levofloxacin or cefuroxime axetil as initial therapy.

STUDY DESIGN

Patients with a primary diagnosis of CAP were enrolled in a multicenter, prospective, randomized, open-label, active-controlled Phase III clinical trial. Both inpatients and outpatients were assigned to 1 of 2 treatment groups: (1) intravenous (i.v.) or p.o. levofloxacin; or (2) i.v. ceftriaxone and/or p.o. cefuroxime axetil.

METHODS

To make legitimate and meaningful cost comparisons between similar types of patients receiving drugs via the same route of administration (i.e., orally), this outpatient economic study examined the resource utilization of the 211 patients enrolled as outpatients who received oral formulations as initial treatment (levofloxacin, 103 patients; cefuroxime axetil, 108 patients). Resource utilization data and clinical trial data were collected concurrently. To generate cost estimates, Medicare cost estimates for resources were multiplied by the resource units used by patients in each treatment arm.

RESULTS

Cost estimates indicated a total cost difference that favored the levofloxacin group (base case: $169; sensitivity analysis: $223 [P = .008]). The results for the base case were not significant (P = .094). In addition, within the cost categories, there was a statistically significant study drug cost differential favoring levofloxacin ($86; P = .0001 for both the base case and sensitivity analysis).

CONCLUSION

Oral levofloxacin is less costly than oral cefuroxime axetil in the outpatient treatment of adults with CAP.

The periplasmic nitrate reductase from Escherichia coli: a heterodimeric molybdoprotein with a double-arginine signal sequence and an unusual leader peptide cleavage site

The periplasmic nitrate reductase, NapA, from Escherichia coli was identified as a 90 kDa molybdoprotein which comigrated during polyacrylamide gel electrophoresis with the di-haem c-type cytochrome, NapB. The DNA sequence of the 5' end of the napA gene and the N-terminal amino acid sequences of both NapA and NapB were determined. The 36 residue leader peptide for NapA includes the double-arginine motif typical of proteins to which complex redox cofactors are attached in the cytoplasm prior to targeting to the periplasm. The pre-NapA leader sequence is both unexpectedly long and, unless two successive proteolysis steps are involved, is cleaved at the unprecedented sequence G-Q-Q-. Nap activity was suppressed during growth in the presence of tungstate and was absent from a mutant unable to synthesise the molybdopterin cofactor.

The expression of Huntingtin-associated protein (HAP1) mRNA in developing, adult and ageing rat CNS: implications for Huntington's disease neuropathology

Using radioactive in situ hybridization, we have mapped the expression of Huntingtin-associated protein (HAP1) mRNA in rat brain at developmental stages (E12-E19, PO-P21), in adult rats (3 months) and in 'aged' (19-21 months) rats. Using two pairs of 45mer oligonucleotide probes specific for HAP1A and a probe which recognizes regions of both the HAP1A and HAP1B mRNA sequences (panHAP1), we find that the expression of HAP1 mRNA is specific to the CNS and restricted predominantly to anatomically connected limbic structures, particularly the amygdala (medial and corticomedial nuclei), the hypothalamus (arcuate, preoptic, paraventricular and lateral hypothalamic area), bed nucleus of the stria terminalis (BNST) and the lateral septal nuclei. HAP1 mRNA was detected in embryos at E12 and displayed a prevalent distribution in the developing limbic structures by E15. In aged, 19-21-months-old, rats there is a downregulation of HAP1 mRNA expression across all CNS loci where HAP1 was previously abundant. The lowest levels of HAP1 mRNA expression corresponded with the areas of greatest pathological cell loss in Huntington's disease (HD); the caudate putamen, globus pallidus and neocortex. These observations support the suggestion that HAP1 plays an important role in the neuropathology of HD.

Oral contraceptive use and protective behavior after missed pills

A three-month prospective study of 103 women initiating oral contraceptive use examined how consistently the women took their pills and whether those who missed pills employed other means to avoid pregnancy. The results showed that 52% took each active pill or never missed more than one pill at a time after the first week of the initial cycle, according to electronic devices that recorded the date and time each pill was removed from the blister pack. Another 21% were protected by behaviors that reduce the risk of pregnancy when two or more consecutive pills have been missed: avoiding coitus for the next seven days (18%) or using backup contraception during that period (3%). The remaining 27% were at increased risk of pregnancy. Predictors of increased risk were receiving low partner support for effective pill use, being unmarried and not considering it especially important to avoid pregnancy. Increased risk was most likely during the first seven days and during the third cycle of pill use.

Revision of a parent-completed development screening tool: Ages and Stages Questionnaires

Examined the Ages and Stages Questionnaires (ASQ), a series of 11 developmental questionnaires designed to be completed by parents and caregivers of young children from 4 to 48 months of age. The ASQ were recently revised and additional psychometric data were gathered. Analyses on over 7,000 questionnaires indicated high test-retest reliability, interobserver reliability, and internal consistency. Concurrent validity using standardized measures yielded on overall agreement of 85%, with a range of 76-91%. Specificity was high across questionnaire intervals while sensitivity was lower and varied across intervals. Use of parent-completed screening tools such as the ASQ is attractive in terms of cost-effectiveness, parental involvement, and flexibility in administration procedures.

The health status of elderly persons in the last year of life: a comparison of deaths by suicide, injury, and natural causes

OBJECTIVES

This study identified health status variables related to suicide by elderly persons and compared the health status of suicide decedents with natural death and injury decedents.

METHODS

Data were obtained from the 1986 National Mortality Followback Survey.

RESULTS

When other variables were controlled for, suicide decedents were significantly more likely than injury decedents to have a history of cancer (odds ratio [OR] = 51.94), moderate (OR = 29.37) or heavy (OR = 22.87) alcohol use, and mental or emotional disorder (OR = 10.91) and to be White (OR = 18.54) and male (OR = 9.12).

CONCLUSIONS

The findings indicate that a history of cancer should be considered as a risk for suicide in the elderly.

Economic evaluation of pharmacist involvement in disease management in a community pharmacy setting

This study evaluated the economic impact of patient-focused pharmacist intervention in the community retail setting in patients with hypertension, diabetes, asthma, and/or hypercholesterolemia. Specially trained pharmacists intervened by providing targeted patient education, performing systematic patient monitoring, offering feedback and behavior modification, and communicating regularly with patients' physicians to enable early intervention for drug-related problems. We evaluated prescription drug costs and total medical costs by comparing claims data from 188 patients enrolled in the program at three intervention pharmacies with data from 401 control patients at five nonparticipating pharmacies from the same retail chain. For all disease states, the average cost per prescription was significantly higher in the group receiving intervention than in the control group. Differences in total monthly prescription costs were significant only for patients with asthma, with higher monthly costs in the group receiving intervention. Substantial savings were demonstrated across all cost analyses for total monthly medical costs. Savings ranged from a conservative estimate of $143.95 per patient per month to $293.39 per patient per month when accounting for the possible influence of age, comorbid conditions, and disease severity. Our data indicate that pharmacist intervention in this community pharmacy-based disease management model substantially reduced monthly health care costs in patients with hypertension, hypercholesterolemia, diabetes, and asthma.

Workshop: the use of muscarinic toxins in the study of muscarinic receptors

One of the most interesting recent developments in the pharmacology of muscarinic receptors has been the finding of small proteins in the venoms of mamba snakes that bind with high affinity and selectivity to different subtypes of muscarinic receptors. In the workshop on muscarinic toxins, the practicalities of isolating, characterising and using these toxins as tools in the study of muscarinic receptors were discussed.

The effects of long-term elevated ozone concentrations on the growth and photosynthesis of Sphagnum recurvum and Polytrichum commune

Although ozone is generally accepted to be an important phytotoxic air pollutant, little is known of its effects on natural and semi-natural vegetation. In this study two bryophyte species, Sphagnum recurvum P. Beauv. and Polytrichum commune Hedw., were exposed to long-term chronic ozone concentrations, i.e. 70-80 ppb (nl 1^-1 ), for 6-9 wk in summer conditions (mean 15°C) and in winter conditions (mean 6.4°C) in open-top chambers (OTC), in the field, and at 15°C and 5°C in controlled-environment chambers, under laboratory conditions. Fumigation with ozone caused a significant reduction in the growth of treated plants in comparison with that of control plants. However, there were differences between species. S. recurvum was more affected than P. commune. In the controlled-environment chambers growth of S. recurvum was reduced under both winter and summer conditions by 21 and 15%, respectively. In the OTCs, S. recurvum growth was reduced (by 17%) only under summer conditions. P. commune growth was only significantly reduced following ozone exposure in the OTCs under winter conditions. Here the growth reduction was by 22%. Net CO₂ assimilation of the two species was also significantly reduced by ozone exposure but only in the OTCs under winter conditions. Net CO₂ assimilation of S. recurvum and P. commune was reduced by 60 and 80%, respectively. The ratio of variable to maximal fluorescence (F_v /F_m ratio) was the least affected of the parameters measured. Only for P. commune fumigated in the OTCs under winter conditions was the F_v /F_m ratio significantly reduced (by 4.4%). Bryophytes, by the very nature of their morphology and physiology are, perhaps, more likely to be susceptible to ozone pollution than higher plants; these results are discussed in relation to their possible ecological significance.